Preparation method of attapulgite-based composite microbial fertilizer

Abstract

The application discloses a preparation method of an attapulgite-based composite microbial fertilizer, and comprises the following steps: preparing biochar powder by subjecting biomass carbon source and purified attapulgite powder to a hydrothermal reaction, mixing the biochar powder with a microbial strain solution and an embedding agent solution, and adding the mixture into a coagulation liquid to obtain the attapulgite-based composite microbial fertilizer. In the application, the attapulgite is modified by using the biomass carbon source, the biomass carbon source is uniformly loaded on the surface of the attapulgite, and the adsorption capacity of the attapulgite is improved. The prepared biochar powder has good adsorption performance and a special multi-stage pore structure, and can better embed the microbial strain. The attapulgite-based composite microbial fertilizer can improve soil fertility, promote crop growth, inhibit plant pathogenic bacteria, and can also enhance the disease resistance and immunity of plants by inducing the endogenous disease resistance potential of the plants, and has great potential in crop cultivation as a new type of microbial fertilizer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of composite microbial fertilizer, more particularly, the present application relates to a preparation method of attapulgite-based composite microbial bacterial fertilizer. BACKGROUND

[0002] At present, the low yield of crops caused by land desertification, drought, saline-alkali soil and other factors is still a problem that needs to be overcome in modern agricultural development. Therefore, the trend of producing high-quality crops by improving the soil environment is unstoppable.

[0003] Attapulgite (ATP), also known as palygorskite, is a kind of hydrous magnesium-aluminum silicate clay mineral with regular pore channels and one-dimensional rod crystal morphology, which is widely used as a wastewater treatment adsorbent. Attapulgite has a large internal and external specific surface area and internal nanometer pore channels, can retain water and fertilizer, and is an ideal soil conditioner and water-retaining agent. Attapulgite has unique dispersibility and high adsorption and decolorization capacity, and has certain thermal stability and catalytic performance. Attapulgite contains various mineral nutrients and can also be used as a fertilizer to act on the field, improve soil properties, and increase soil fertility, thereby increasing the survival rate and yield of crops. However, due to its limited adsorption capacity, it is not easy to separate from water after adsorption, and its strong hydrophilicity results in weak affinity for organic pollutants, so it is necessary to modify attapulgite.

[0004] Microorganisms refer to tiny organisms that cannot be seen by the naked eye, including bacteria, fungi, viruses and the like, which widely exist in nature. The main microorganisms include Bacillus subtilis, gelatin-like Bacillus, Brevibacillus laterosporus, Bacillus amyloliquefaciens, Bacillus megaterium, Bacillus licheniformis, Bacillus methylotrophicus, Bacillus velezensis, Bacillus polymyxa, Bacillus cereus, Bacillus thuringiensis, Trichoderma harzianum, Paecilomyces lilacinus and the like, which widely exist in nature and play an important role in the growth and development of plants, and can promote the growth of plants. Microorganisms can also decompose harmful substances in the soil and reduce the harm of toxic substances in the soil to plants. Therefore, in agricultural production, reasonable use of the role of microorganisms can improve the yield and quality of crops. The microorganism immobilization method mainly includes embedding method, adsorption method and covalent cross-linking method, and the adsorption method is the most commonly used because of its simple operation. Sodium alginate, gelatin and agar are the most widely used embedding agents, however, poor mechanical strength and short service life limit their industrial application. SUMMARY

[0005] An object of the present application is to solve at least the above problems and / or defects, and to provide at least the advantages to be described later.

[0006] In order to achieve the objects and other advantages of the present application, a preparation method of attapulgite-based composite microbial fertilizer is provided, comprising the following steps:

[0007] Step one, uniformly mix the biomass carbon source solution and the purified attapulgite powder, place in a constant temperature oscillator to oscillate, form a uniform solution, then transfer to a hydrothermal reaction kettle, carry out hydrothermal reaction, after the reaction is complete, the obtained black brown product is washed with anhydrous ethanol and distilled water until there is no obvious color change, dry to obtain black brown biochar powder;

[0008] Step two, mix the biochar powder and sodium dihydrogen phosphate, dissolve by adding distilled water, add to the embedding agent solution, oscillate on the constant temperature oscillator, ultrasonic treatment, obtain a mixed solution; dissolve the microbial strain in the distilled water irradiated by ultraviolet light, seal, oscillate on the constant temperature oscillator, then add to the aforementioned mixed solution, oscillate on the constant temperature oscillator, obtain a biochar / microorganism / embedding agent solution;

[0009] Step three, add the biochar / microorganism / embedding agent solution to the coagulation liquid, filter to obtain black hydrogel microspheres, after washing with water, place in a refrigerator to freeze, then place in a freeze dryer to dry, obtain the attapulgite-based composite microbial fertilizer.

[0010] Preferably, in the step one, the preparation method of the purified attapulgite powder is as follows: finely grind the attapulgite and sieve, stir into mud with distilled water, place in a refrigerator to freeze for 3-5 h, take out and place for 2-4 h, dry, naturally cool to room temperature, finely grind and sieve to obtain attapulgite powder, then dissolve sodium pyrophosphate in distilled water under stirring, heat to 35-45℃, continue to stir for 20-40 min, then add the attapulgite powder to the above solution under high-speed stirring, stir for 50-70 min, then stand for 20-40 min, then add phosphoric acid until no bubbles escape, ultrasonic treatment, then high-speed stir at 35-45℃ for 4-6 h, age at room temperature for 20-28 h, remove the supernatant and the bottom sand, centrifuge, wash with distilled water until neutral, dry, finely grind and sieve to obtain the purified attapulgite powder.

[0011] Preferably, the mass-volume ratio of the sodium pyrophosphate, the attapulgite powder and the distilled water is 0.5-0.7 g:20 g:300-500 mL; the ultrasonic treatment has an ultrasonic power of 300-600 W, a frequency of 60-100 kHz, and a treatment time of 20-40 min; the sieve has a mesh number of 180-230 meshes; the centrifugation has a rotation speed of 2000-4000 r / min and a centrifugation time of 15-25 min; the drying has a temperature of 100-120℃ and a time of 4-12 h.

[0012] Preferably, in the step one, the biomass carbon source is one or more of glucose, fructose, sucrose, maltose, starch, cellulose; the concentration of the biomass carbon source solution is 0.1-0.3 mol / L; the mass ratio of the biomass carbon source to the purified attapulgite powder is 2-4:2; the hydrothermal reaction temperature is 170-190℃, the reaction time is 22-26 h; the drying temperature is 80-100℃, and the drying time is 3-5 h.

[0013] Preferably, in the step one and step two, the temperature of the constant temperature oscillator is 15-25℃, the oscillation speed is 160-200 r / min, and the oscillation time is 1-14 h.

[0014] Preferably, in the step two, the mass-volume ratio of the biochar powder, sodium dihydrogen phosphate, distilled water and embedding agent solution is 0.3 g:0.3-0.5 g:40-60 mL:80-120 mL; the mass-volume ratio of the embedding agent in the embedding agent solution to distilled water is 1 g:80-120 mL, and the embedding agent is one or more of sodium alginate, agar and gelatin; the ultrasonic power for ultrasonic treatment is 300-600 W, the frequency is 60-100 kHz, and the treatment time is 20-40 min.

[0015] Preferably, in the step two, the microbial strain is one or more of Bacillus subtilis, Bacillus mycoides, Bacillus laterosporus, Bacillus amyloliquefaciens, Bacillus megaterium, Bacillus licheniformis, Bacillus methylotrophicus, Bacillus velezensis, Bacillus polymyxa, Bacillus cereus, Bacillus thuringiensis, Trichoderma harzianum and Paecilomyces lilacinus; the mass-volume ratio of the biochar powder, the microbial strain and the distilled water irradiated by ultraviolet light is 0.3 g:0.0004-0.0006 g:40-60 mL.

[0016] Preferably, in the step three, the preparation method of the coagulation liquid is as follows: chitosan is added to an acetic acid solution, and a magnetic stirrer is used for stirring until the chitosan is completely dissolved, then calcium chloride is added and stirred to dissolve, to obtain the coagulation liquid.

[0017] Preferably, the concentration of the acetic acid solution is 2-4 wt%; the mass-volume ratio of the chitosan, calcium chloride and acetic acid solution is 0.2-0.6 g:0.8-1.2 g:100-300 mL; and the rotation speed of the magnetic stirrer is 20-40 r / min.

[0018] Preferably, in the step three, the mass ratio of the biochar powder in the biochar / microorganism / embedding agent solution to the chitosan in the coagulation liquid is 0.3:0.2-0.6; the water washing frequency is 2-4 times; the refrigerator freezing time is 4-8 h; and the freeze-drying time is 10-14 h.

[0019] The present application at least comprises the following beneficial effects: the present application discloses a preparation method of attapulgite-based composite microbial fertilizer, biomass carbon source is used to modify attapulgite, the biomass carbon source is uniformly loaded on the surface of attapulgite, the adsorption capacity of attapulgite is improved, the prepared biochar powder has good adsorption performance and special hierarchical pore structure, and can better embed microbial strains. The attapulgite-based composite microbial fertilizer can improve soil fertility, promote crop growth, inhibit plant pathogenic bacteria, enhance plant disease resistance and immunity by inducing endogenous disease resistance of plants, effectively inhibit or alleviate various plant diseases, reduce the use amount of chemical fertilizers and pesticides, and is safe and efficient. As a new type of microbial fertilizer, the attapulgite-based composite microbial fertilizer has great potential in crop cultivation.

[0020] Other advantages, objects, and features of the present application will be apparent from the following specification, and will be understood by those skilled in the art. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Scanning electron microscope images of glucose (a), purified attapulgite powder prepared in Comparative Example 1 (b), and biochar powder prepared in Comparative Example 2 (c);

[0022] Figure 2 Infrared spectra of glucose, purified attapulgite powder prepared in Comparative Example 1, and biochar powder prepared in Comparative Example 2;

[0023] Figure 3 Infrared spectra of attapulgite-based composite microbial fertilizers prepared in Examples 1-3 of the present application;

[0024] Figure 4 Scanning electron microscope images of cross sections (a, b, c) and the whole (e, f, g) of the attapulgite-based composite microbial fertilizer prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below with reference to examples, so that those skilled in the art can implement the present application according to the description.

[0026] It should be understood that the terms such as "have", "contain", and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0027] Example 1

[0028] A preparation method of attapulgite-based composite microbial fertilizer comprises the following steps:

[0029] Step one, the attapulgite is ground to pass through a 200 mesh screen, stirred into a mud with distilled water, placed in a freezer for 4h, taken out and placed for 3h, dried at 110℃ for 12h, naturally cooled to room temperature, ground to pass through a 200 mesh screen, to obtain attapulgite powder, then 0.6g sodium pyrophosphate is dissolved in 400mL distilled water under stirring, heated to 40℃, continue to stir for 30min, then 20g attapulgite powder is added to the above solution under high speed stirring, stirred for 60min, then placed for 30min, then add phosphoric acid until no bubbles escape, ultrasonic treatment for 30min under power of 500W and frequency of 80kHz, high speed stirring for 5h at 40℃, aging for 24h at room temperature, remove the supernatant and the bottom sand, centrifuged at 3000r / min for 20min, washed to neutral with distilled water, dried at 105℃ for 4h, ground to pass through a 200 mesh screen, to obtain purified attapulgite powder;

[0030] Step two, 0.9g glucose is dissolved in distilled water to prepare a glucose solution with a concentration of 0.2mol / L, 0.6g purified attapulgite powder is added and mixed uniformly, placed in a constant temperature oscillator at 20℃ and 180r / min to form a uniform solution, then transferred to a hydrothermal reaction kettle, hydrothermal reaction at 180℃ for 24h, after the reaction is completed, the obtained black-brown product is washed with anhydrous ethanol and distilled water until there is no obvious color change, dried at 90℃ for 4h, to obtain black-brown biochar powder;

[0031] Step three, weigh 1g sodium alginate and dissolve in 100mL distilled water, stir with a magnetic stirrer at 30r / min until completely dissolved, to obtain a sodium alginate solution; mix 0.3g biochar powder and 0.4g sodium dihydrogen phosphate, add 50mL distilled water to dissolve, add to the sodium alginate solution, oscillate on a constant temperature oscillator at 20℃ and 180r / min for 12h, ultrasonic treatment for 30min under power of 500W and frequency of 80kHz, to obtain a mixed solution; then dissolve 0.0005g Bacillus velezensis strain in 50mL distilled water irradiated by ultraviolet light, seal, oscillate on a constant temperature oscillator at 20℃ and 180r / min for 12h, add to the above mixed solution, oscillate on a constant temperature oscillator at 20℃ and 180r / min for 1h, to obtain a biochar / microorganism / embedding agent solution;

[0032] Step four, add 0.4g chitosan to 200mL 3wt% acetic acid solution, stir with a magnetic stirrer at 30r / min until the chitosan is completely dissolved, then add 1g calcium chloride, stir to dissolve, to obtain a coagulation liquid;

[0033] Step five, the biochar / microorganism / encapsulant solution obtained in step three is added to the coagulation solution obtained in step four, and black hydrogel microspheres are obtained by filtration, washed with water for 3 times, placed in a refrigerator for 6h, and then placed in a freeze dryer for drying for 12h to obtain attapulgite-based composite microbial fertilizer.

[0034] Example 2

[0035] Bacillus velezensis is replaced by Bacillus polymyxa, and the remaining steps are the same as those in Example 1.

[0036] Example 3

[0037] Bacillus velezensis is replaced by Bacillus amyloliquefaciens, and the remaining steps are the same as those in Example 1.

[0038] Comparative Example 1

[0039] A method for preparing purified attapulgite powder includes the following steps: grinding attapulgite to pass through a 200-mesh screen, stirring it into a paste with distilled water, placing it in a refrigerator for 4h, taking it out and placing it for 3h, drying it at 110℃ for 12h, naturally cooling it to room temperature, grinding it to pass through a 200-mesh screen to obtain attapulgite powder, then dissolving 0.6g of sodium pyrophosphate in 400mL of distilled water under stirring, heating to 40℃, continuing to stir for 30min, then adding 20g of attapulgite powder to the above solution under high-speed stirring, stirring for 60min and then standing for 30min, then adding phosphoric acid until no bubbles escape, ultrasonic treatment at a power of 500W and a frequency of 80kHz for 30min, high-speed stirring at 40℃ for 5h, aging at room temperature for 24h, removing the supernatant and the bottom sand, centrifuging at 3000r / min for 20min, washing with distilled water until neutral, drying at 105℃ for 4h, and grinding to pass through a 200-mesh screen to obtain purified attapulgite powder.

[0040] Comparative Example 2

[0041] A method for preparing biochar powder includes the following steps:

[0042] Step one, the attapulgite is ground to pass through a 200 mesh screen, stirred into a paste with distilled water, placed in a freezer for 4h, taken out and left to stand for 3h, dried at 110℃ for 12h, naturally cooled to room temperature, ground to pass through a 200 mesh screen, 0.6g sodium pyrophosphate is dissolved in 400mL distilled water under stirring, heated to 40℃, continue to stir for 30min, then 20g attapulgite powder is added to the above solution under high speed stirring, stirred for 60min, then left to stand for 30min, then add phosphoric acid until no bubbles escape, ultrasonic treatment for 30min at a power of 500W and a frequency of 80kHz, high speed stirring for 5h at 40℃, aged for 24h at room temperature, remove the supernatant and the bottom sand, centrifuged at 3000r / min for 20min, washed to neutral with distilled water, dried at 105℃ for 4h, ground to pass through a 200 mesh screen, to obtain purified attapulgite powder;

[0043] Step two, 0.9g glucose is dissolved in distilled water to prepare a glucose solution with a concentration of 0.2mol / L, 0.6g purified attapulgite powder is added and mixed evenly, placed in a constant temperature oscillator at 20℃ and 180r / min to form a uniform solution, then transferred to a hydrothermal reaction kettle, hydrothermal reaction at 180℃ for 24h, after the reaction is complete, the obtained black brown product is washed with anhydrous ethanol and distilled water until there is no obvious color change, dried at 90℃ for 4h to obtain black brown biochar powder.

[0044] Figure 1 The scanning electron microscope images of glucose (a), purified attapulgite powder prepared in Comparative Example 1 (b) and biochar powder prepared in Comparative Example 2 (c). As can be seen from figure (b), the purified attapulgite has a rich pore structure, mainly rod-shaped and granular structure, smooth surface with edges and corners, and figure (a) and (c) show that the glucose is uniformly loaded on the surface of the attapulgite, and the prepared biochar powder has a special hierarchical pore structure, which can better embed microbial strains.

[0045] Figure 2 The infrared spectra of glucose, purified attapulgite powder prepared in Comparative Example 1 and biochar powder prepared in Comparative Example 2. It can be seen that the biochar has characteristic peaks of glucose and attapulgite, and no other impurity peaks, indicating that the glucose and attapulgite are compounded by physical adsorption, and the biochar powder is successfully prepared; Figure 3 The infrared spectra of attapulgite-based composite microbial fertilizer prepared in Examples 1-3 of the application. It can be seen that the main characteristic peaks of the attapulgite-based composite microbial fertilizer of different microbial strains are roughly similar, there are no other impurity peaks, and the infrared spectrum is similar to that of the biochar powder, indicating that no chemical change occurs, but only physical adsorption and mutual compounding.

[0046] Figure 4 The scanning electron microscope images of the cross section (a, b, c) and the whole (e, f, g) of the attapulgite-based composite microbial fertilizer prepared in Example 1 of the present application are shown in the figure. As can be seen from the figure (a, b, c), the cross section is not flat, having rod-like and rod-like structures, indicating that the structures of attapulgite and microbial strains are attached in the pore size of biochar; in the figure (e, f, g), no microbial strains are observed on the surface of biochar, indicating that the microbial strains are embedded inside and there is no delamination phenomenon.

[0047] The attapulgite-based composite microbial fertilizer prepared in Example 1 was added to the natural soil to make a microbial soil under room temperature, and the natural soil without the addition of the microbial fertilizer was used as a control, zucchini and cucumber were planted in the microbial soil and the natural soil, and the germination state and stem height of the two plants were observed. According to the comparison of the germination state, the zucchini and cucumber in the microbial soil germinated more than those in the natural soil when the seeds germinated, and grew better. Under the same conditions, the stem height of the plants was recorded after 20 days of growth, and the results are shown in Table 1. It can be seen that with the growth of zucchini and cucumber, the zucchini and cucumber in the microbial soil gradually showed more growth advantages than those in the natural soil, and the appearance and growth conditions were more regular, and the advantages were more obvious.

[0048] Table 1

[0049]

[0050]

[0051] The above experimental results show that the attapulgite-based composite microbial fertilizer of the present application can improve soil fertility, promote crop growth, inhibit plant pathogenic bacteria, enhance plant disease resistance by inducing the endogenous disease resistance potential of plants, enhance plant immunity, effectively inhibit or alleviate various plant diseases, and reduce the use amount of chemical fertilizers and pesticides, which is safe and efficient.

[0052] Although the embodiments of the present application have been disclosed as above, they are not limited to the application listed in the specification and the embodiments, and can be fully applied to various fields suitable for the present application, and additional modifications can be easily realized by those skilled in the art, and therefore the present application is not limited to specific details and the examples shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A method for preparing an attapulgite-based composite microbial bacterial fertilizer, characterized in that, The method comprises the following steps: Step one, the biomass carbon source solution and purified attapulgite powder are mixed uniformly, placed in a constant temperature oscillator to form a uniform solution, then transferred to a hydrothermal reactor for hydrothermal reaction, after the reaction is completed, the obtained black brown product is washed with anhydrous ethanol and distilled water until the color has no obvious change, dried to obtain black brown biochar powder; wherein the biomass carbon source is glucose; the concentration of the biomass carbon source solution is 0.1-0.3 mol / L; the mass ratio of the biomass carbon source to the purified attapulgite powder is 3-4:2; the hydrothermal reaction temperature is 170-190 DEG C, the reaction time is 22-26h; the drying temperature is 80-100 DEG C, and the drying time is 3-5h; Step two, the biochar powder and sodium dihydrogen phosphate are mixed, added with distilled water to dissolve, added to the embedding agent solution, oscillated on a constant temperature oscillator, ultrasonic treated to obtain a mixed solution; the microbial strain is dissolved in distilled water irradiated by ultraviolet light, sealed, oscillated on a constant temperature oscillator, then added to the mixed solution, oscillated on a constant temperature oscillator to obtain a biochar / microorganism / embedding agent solution; wherein the embedding agent is sodium alginate; Step three, the biochar / microorganism / embedding agent solution is added to a coagulation liquid, filtered to obtain black hydrogel microspheres, washed with water, placed in a refrigerator for freezing, then placed in a freeze dryer for drying to obtain an attapulgite-based composite microbial fertilizer; wherein the preparation method of the coagulation liquid is that chitosan is added to acetic acid solution, stirred with a magnetic stirrer until the chitosan is completely dissolved, then calcium chloride is added and stirred to dissolve to obtain the coagulation liquid.

2. A process for the preparation of attapulgite-based composite microbial bacterial manure as claimed in claim 1, wherein, In the step one, the preparation method of the purified attapulgite powder is that the attapulgite is finely ground and sieved, stirred into a mud state with distilled water, placed in a refrigerator for freezing for 3-5h, taken out and placed for 2-4h, dried, naturally cooled to room temperature, finely ground and sieved to obtain attapulgite powder, then sodium pyrophosphate is dissolved in distilled water under stirring, heated to 35-45 DEG C, continuously stirred for 20-40min, then the attapulgite powder is added to the above solution under high-speed stirring, stirred for 50-70min, then placed for 20-40min, then phosphoric acid is added until no bubbles escape, ultrasonic treated, then high-speed stirred at 35-45 DEG C for 4-6h, aged at room temperature for 20-28h, removed the supernatant and the bottom sand, centrifuged, washed with distilled water until neutral, dried, finely ground and sieved to obtain the purified attapulgite powder.

3. The method for preparing an attapulgite-based composite microbial fertilizer as described in claim 2, characterized in that, The mass-volume ratio of the sodium pyrophosphate, the attapulgite powder and the distilled water is 0.5-0.7g:20g:300-500mL; the ultrasonic treatment has an ultrasonic power of 300-600W, a frequency of 60-100kHz, and a treatment time of 20-40min; the sieving has a mesh number of 180-230 meshes; the centrifugation has a rotation speed of 2000-4000r / min and a centrifugation time of 15-25min; the drying has a temperature of 100-120 DEG C and a time of 4-12h.

4. A process for the preparation of attapulgite based composite microbial bacterial manure as claimed in claim 1, wherein, The constant temperature oscillator temperature is 15-25 DEG C, the oscillation speed is 160-200 r / min, and the oscillation time is 1-14 h in the step one and the step two.

5. A process for the preparation of attapulgite based composite microbial bacterial manure as claimed in claim 1, wherein, The mass-volume ratio of the biochar powder, the sodium dihydrogen phosphate, the distilled water and the embedding agent solution is 0.3 g:0.3-0.5 g:40-60 mL:80-120 mL in the step two; the mass-volume ratio of the embedding agent and the distilled water in the embedding agent solution is 1 g:80-120 mL; the ultrasonic power is 300-600 W, the frequency is 60-100 kHz, and the processing time is 20-40 min in the ultrasonic treatment.

6. A process for the preparation of attapulgite based composite microbial bacterial manure as claimed in claim 1, wherein, The microorganism strain is one or more of Bacillus subtilis, Bacillus mycoides, Bacillus laterosporus, Bacillus amyloliquefaciens, Bacillus megaterium, Bacillus licheniformis, Bacillus methylotrophicus, Bacillus velezensis, Bacillus polymyxa, Bacillus cereus, Bacillus thuringiensis, Trichoderma harzianum and Paecilomyces lilacinus in the step two; the mass-volume ratio of the biochar powder, the microorganism strain and the distilled water irradiated by ultraviolet light is 0.3 g:0.0004-0.0006 g:40-60 mL.

7. A process for the preparation of attapulgite based composite microbial bacterial manure as claimed in claim 1, wherein, The concentration of the acetic acid solution is 2-4 wt% in the preparation method of the coagulation liquid; the mass-volume ratio of the chitosan, the calcium chloride and the acetic acid solution is 0.2-0.6 g:0.8-1.2 g:100-300 mL; and the rotating speed of the magnetic stirrer is 20-40 r / min.

8. A process for the preparation of attapulgite based composite microbial bacterial manure as claimed in claim 1, wherein, The mass ratio of the biochar powder in the biochar / microorganism / embedding agent solution and the chitosan in the coagulation liquid is 0.3:0.2-0.6 in the step three; the water washing times are 2-4 times; the refrigerator freezing time is 4-8 h; and the freeze-drying time is 10-14 h.

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